The present invention relates to a storage system, and relates in particular to technology for switching between processors that perform processing in response to commands in a storage system.
Data processing systems including a host computer and a storage system are utilized in various applications. Here, a storage system refers to a system composed of at least one storage node that has disks for storing data and a controller for controlling the disks. Typically, within a storage node there are configured one or a plurality of logical memory areas (called “logical units” for example) with the disks. The host computer issues a command addressed to a logical unit configured within a storage node of the storage system, while executing data processing tasks. Within the storage node that received the command from the host computer, a processor within the controller (e.g. a CPU core) carries out processing in response to the command.
In a storage system of this kind, an excessive load may be imposed on a particular processor within a particular storage node, due to an increase in the amount of data stored in a logical unit, or an increase in access frequency by the host computer.
Technology for migrating data from a logical unit in a first storage node to a logical unit in a second storage node in a storage system has been disclosed (e.g. JP2000-187608A). With this technology, after data has been migrated, commands from the host computer are handled by the second storage node. Thus, processing in response to a command from the host computer being executed by the processor in the first storage node prior to data migration will, after data migration, now be executed by the processor in the second storage node. In the event of excessive load on a particular processor as mentioned above, by switching among processors executing processing in response to commands from the host computer in this way, the processing load can be distributed throughout the system.
A problem with the conventional technology discussed above is that, when switching between processors executing processing in response to a command, it is necessary to migrate the data and to modify various settings in association therewith, making processing extremely complex.